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Abstract:

An object of the present invention is to protect a battery pack in the
event of a vehicle rear impact in an electric car in which the battery
pack is arranged between rear side members arranged at a vehicle rear
portion.
The present invention provides a battery pack mounting structure for
electric cars in which a pair of rear side members having a front
portion, a rear portion, and a rising portion are arranged at both
vehicle-widthwise side portions, intermediate portions of the respective
rear side members are coupled to each other by a cross member, and a
battery pack is mounted on a vehicle body by a sub-frame that is coupled
to the respective rear side members and the cross member, wherein the
cross member is arranged at a position below a bent portion that connects
the rising portion and the rear portion of each of the rear side members,
the sub-frame includes a ring-like support frame that extends in a
horizontal direction and surrounds an outer periphery of the battery
pack, and a front side portion and both vehicle-widthwise side portions
of the support frame are respectively coupled to the cross member and the
rear portions of the respective rear side members by coupling portions.

Claims:

1. A battery pack mounting structure for electric cars, comprising: a
pair of rear side members extending in a vehicle longitudinal direction
and having a front portion, a rear portion that is arranged at a position
above the front portion, and a rising portion that connects both portions
are arranged at both vehicle-widthwise side portions, intermediate
portions of the respective rear side members are coupled to each other by
a cross member that extends in a vehicle width direction, and a battery
pack is mounted on a vehicle body by a sub-frame that is coupled to the
respective rear side members and the cross member, wherein the cross
member is arranged at a position below a bent portion that connects the
rising portion and the rear portion of each of the rear side members, the
sub-frame includes a ring-like support frame that extends in a horizontal
direction and surrounds an outer periphery of the battery pack, and a
front side portion and both vehicle-widthwise side portions of the
support frame are respectively coupled to the cross member and the rear
portions of the respective rear side members by coupling portions.

2. The battery pack mounting structure for electric cars according to
claim 1, wherein the battery pack includes a flange portion that
surrounds the battery pack in a ring-like shape, and that is coupled to
the support frame of the sub-frame.

3. The battery pack mounting structure for electric cars according to
claim 2, wherein the support frame includes a pair of side member
portions that extend in directions along the respective rear side
members, and a front member portion and a rear member portion that extend
in the vehicle width direction, the battery pack is arranged at an offset
position toward one side of the pair of side member portions in the
vehicle width direction on an inner side of the support frame, and a
bracket that couples the front member portion and the rear member portion
is arranged in a space that is formed on the other side of the pair of
side member portions on the inner side of the support frame by offsetting
the battery pack.

4. The battery pack mounting structure for electric cars according to
claim 1, wherein a fuel tank is arranged in front of the battery pack, a
filler pipe that extends to a vehicle-widthwise outer side from the rear
side member is coupled to the fuel tank, and the filler pipe extends to
the vehicle-widthwise outer side from the rear side member through a
space sandwiched between the rear side member and the support frame in a
vehicle vertical direction.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to Japanese Patent
Application No. 2012-068587 filed Mar. 26, 2012, the content of which is
incorporated by reference herein its entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a battery pack mounting structure
for electric cars, and more particularly, relates to a battery pack
mounting structure for electric cars for use to protect a battery pack
mounted on an electric car which runs by a motor driving force from an
impact force in the event of a rear impact.

[0004] 2. Description of Related Art

[0005] Electric cars which run by a motor driving force need to have a
larger battery capacity so as to run longer distances. At this point,
when the battery capacity increases, a larger and heavier battery pack is
required to store a battery. Thus, the battery pack is often mounted in a
lower portion of a vehicle or a rear portion of the vehicle.

[0006] As a conventional battery pack mounting structure for electric
cars, Japanese Patent Laid-Open No. 2004-161158 discloses a structure in
which a plurality of battery packs are mounted in a longitudinal
direction on the lower side of a rear floor, wherein a battery pack on
the front side is mounted at a lower height above the ground than a
battery pack on the rear side.

[0007] In the publication, a mount frame for mounting the battery packs on
a vehicle body is composed of a front portion that extends in the vehicle
longitudinal direction, a rear portion that is arranged at a position
above the front portion and extends in the vehicle longitudinal
direction, and a rising portion that connects both portions and extends
in a vehicle vertical direction, and is formed in a step-like shape in
side view such that the front portion having a front-side battery
mounting surface is located at a lower height above the ground than the
rear portion having a rear-side battery mounting surface.

SUMMARY OF THE INVENTION

[0008] In the above publication, however, since the mount frame for
mounting the battery packs on the vehicle body is bent in the vehicle
vertical direction at a vehicle-longitudinal intermediate portion, the
mount frame is deformed in the vehicle vertical direction when an impact
force is applied from the vehicle rear side in the event of a vehicle
rear impact. Thus, in the battery pack mounting structure according to
the above publication, the battery pack is difficult to sufficiently
protect by the mount frame.

[0009] Also, in the above publication, while both vehicle-widthwise end
portions of the mount frame are coupled to a pair of rear side members
that extend in the vehicle longitudinal direction, the rear side members
include a rising portion that extends upward at a vehicle-longitudinal
intermediate portion. Thus, when an impact force is applied from the
vehicle rear side, a rear portion of the rising portion is deformed so as
to project to the vehicle upper side, so that the longitudinal length is
reduced. Accordingly, in the battery pack mounting structure according to
the above publication, there is a risk that the battery pack moves toward
the vehicle front side so as to come into contact with another in-vehicle
part.

[0010] It is an object of the present invention to protect a battery pack
in the event of a vehicle rear impact in an electric car in which the
battery pack is arranged between rear side members arranged at a vehicle
rear portion.

[0011] The present invention provides a battery pack mounting structure
for electric cars in which a pair of rear side members extending in a
vehicle longitudinal direction and having a front portion, a rear portion
that is arranged at a position above the front portion, and a rising
portion that connects both portions are arranged at both
vehicle-widthwise side portions, intermediate portions of the respective
rear side members are coupled to each other by a cross member that
extends in a vehicle width direction, and a battery pack is mounted on a
vehicle body by a sub-frame that is coupled to the respective rear side
members and the cross member, wherein the cross member is arranged at a
position below a bent portion that connects the rising portion and the
rear portion of each of the rear side members, the sub-frame includes a
ring-like support frame that extends in a horizontal direction and
surrounds an outer periphery of the battery pack, and a front side
portion and both vehicle-widthwise side portions of the support frame are
respectively coupled to the cross member and the rear portions of the
respective rear side members by coupling portions.

[0012] In the present invention, the sub-frame for mounting the battery
pack on the vehicle body includes the ring-like support frame that
extends in the horizontal direction and surrounds the outer periphery of
the battery pack. Thus, since the sub-frame does not include a vertical
bent portion, the sub-frame can be formed into such a shape that is
difficult to bend in a vehicle vertical direction and difficult to
compress in the vehicle-longitudinal length when an impact force is
applied to the sub-frame in the vehicle longitudinal direction.

[0013] Since the front side portion of the support frame is coupled to the
cross member by the coupling portion, the sub-frame transmits a forward
force acting on the support frame to the cross member arranged at a
position below the bent portions that connect the rising portions and the
rear portions of the rear side members, and can thereby suppress
deformation of the rear side members at the bent portions when an impact
force is applied from the vehicle rear side.

[0014] Also, in the sub-frame, since the both vehicle-widthwise side
portions of the support frame are coupled to the rear portions of the
rear side members by the coupling portions, the rear side members can be
reinforced by the support frame, and the rear side members can be thereby
prevented from being bent in the vehicle vertical direction when
receiving a force in the vehicle longitudinal direction.

[0015] Thus, the rear side members are deformed at the bent portions that
connect the rising portions and the rear portions in the event of a
vehicle rear impact, so that the battery pack can be prevented from
colliding with an in-vehicle part arranged in front thereof.

[0016] Therefore, in the present invention, the battery pack can be
protected in the event of a vehicle rear impact in the electric car in
which the battery pack is arranged between the rear side members arranged
at a vehicle rear portion.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 is a side view of an electric car (embodiment);

[0018]FIG. 2 is a bottom view of a vehicle rear portion of the electric
car (embodiment);

[0019]FIG. 3 is a left side view of the vehicle rear portion of the
electric car (embodiment);

[0020]FIG. 4 is an assembly perspective view of a battery pack and a
sub-frame (embodiment); and

[0021] FIG. 5 is a sectional perspective view of the vehicle rear portion
of the electric car (embodiment).

DETAILED DESCRIPTION

[0022] In the following, an embodiment of the present invention will be
described based on the drawings.

[0023] FIGS. 1 to 5 show the embodiment of the present invention. In FIG.
1, reference numeral 1 denotes an electric car, 2 a vehicle body, 3 an
engine compartment, 4 a vehicle interior, 5 a trunk, 6 a front wheel, and
7 a rear wheel. In the electric car 1, a dash panel 8 that extends in a
vehicle width direction is arranged at a front portion of the vehicle
body 2. In the electric car 1, a pair of front side members 9 and 10 that
extend in a vehicle longitudinal direction are arranged at both widthwise
side portions of a center portion of the vehicle body 2, and a pair of
rear side members 11 and 12 that extend in the vehicle longitudinal
direction are arranged at both widthwise side portions of a rear portion
of the vehicle body 2 as shown in FIG. 2.

[0024] The engine compartment 3 is formed on the front side of the dash
panel 8 at the front portion of the vehicle body 2. A front floor panel
13 is attached to the pair of front side members 9 and 10 at the center
portion of the vehicle body 2, and the vehicle interior 4 is formed at an
upper portion of the front floor panel 13. A rear floor panel 14
connected to the front floor panel 13 is attached to the pair of rear
side members 11 and 12 at the rear portion of the vehicle body 2, and a
portion of the vehicle interior 4 is formed at a front-side upper portion
and the trunk 5 is formed at a rear-side upper portion of the rear floor
panel 14.

[0025] An engine 15 that drives a power generator is arranged in the
engine compartment 3. The front floor panel 13 is formed in a
substantially flat shape, and a front seat 16 is arranged in the vehicle
interior 4 at the upper portion. The rear floor panel 14 is composed of a
vertical wall portion 17 that rises upward from a rear end of the front
floor panel 13, and a horizontal wall portion 18 that extends to the
vehicle rear side from an upper end of the vertical wall portion 17 as
shown in FIG. 3. A rear end of the horizontal wall portion 18 is attached
to a rear panel 19 of the vehicle body 2. In the horizontal wall portion
18, a rear seat 20 is arranged at a front-side upper portion, and a fuel
tank 21 that stores fuel of the engine 15 is arranged at a front-side
lower portion. The trunk 5 is formed at an upper portion of the
horizontal wall portion 18 between the rear seat 20 and the rear panel
19.

[0026] A filler pipe 22 that extends to a vehicle-widthwise outer side
from the lower side of the rear side member 12 on the left side is
coupled to the fuel tank 21. A filler cap 23 is removably attached to a
distal end of the filler pipe 22.

[0027] In the electric car 1, the pair of rear side members 11 and 12 that
extend in the vehicle longitudinal direction are arranged at the both
vehicle-widthwise side portions at the rear portion of the vehicle body 2
as shown in FIG. 2. The rear side member 11 on the right side includes a
front portion 24, a rear portion 25 that is arranged at a position above
and backward of the front portion 24, and a rising portion 26 that
connects the front portion 24 and the rear portion 25 as shown in FIGS. 2
and 3. A bent portion 27 that connects a rear end of the rising portion
26 and a front end of the rear portion 25 is provided at an intermediate
portion of the right rear side member 11. The left rear side member 12
includes a front portion 28, a rear portion 29 that is arranged at a
position above and backward of the front portion 28, and a rising portion
30 that connects the front portion 28 and the rear portion 29 as shown in
FIG. 2. A bent portion 31 that connects a rear end of the rising portion
30 and a front end of the rear portion 29 is provided at an intermediate
portion of the left rear side member 12.

[0028] The intermediate portions of the respective rear side members 11
and 12 are coupled to each other by a cross member 32 that extends in the
vehicle width direction as shown in FIG. 3. One end of the cross member
32 is arranged at a position below an upper-side edge portion of the bent
portion 27 that connects the rising portion 26 and the rear portion 25 of
the right rear side member 11, and the other end of the cross member 32
is arranged at a position below an upper-side edge portion of the bent
portion 31 that connects the rising portion 30 and the rear portion 29 of
the left rear side member 12. An intermediate portion of the horizontal
wall portion 18 of the above rear floor panel 14 is attached to the cross
member 32. The above fuel tank 21 is arranged below the horizontal wall
portion 18 of the rear floor panel 14 on the front side from the cross
member 32.

[0029] In the electric car 1, suspension arms 33 and 34 that respectively
extend in the vehicle longitudinal direction are also arranged on the
lower side of the rising portions 26 and 30 of the respective rear side
members 11 and 12 as shown in FIG. 2. Intermediate portions of the
respective suspension arms 33 and 34 are coupled together by a suspension
beam 35 on the lower side of the cross member 32, and the respective
suspension arms 33 and 34 are supported by fulcrums 36 and 37 at front
ends on the lower side of the rising portions 26 and 30. Accordingly, the
respective suspension arms 33 and 34 are integrated by the suspension
beam 35, and are supported by the rising portions 26 and 30 so as to be
vertically rotatable on rear end sides around the fulcrums 36 and 37.

[0030] In the electric car 1, a battery pack 38 is arranged at the rear
portion of the vehicle body 2 as shown in FIGS. 2 and 3. The fuel tank 21
is arranged in front of the battery pack 38. The battery pack 38 is
charged by the power generator driven by the engine 15. An insertion hole
39 through which the battery pack 38 is inserted from the lower side is
formed in the horizontal wall portion 18 of the rear floor panel 14 that
forms the trunk 5 on the rear side from the cross member 32. A rolled
cover panel 40 that surrounds the insertion hole 39 is attached to the
upper side of the horizontal wall portion 18. A service lid 42 is
removably attached to an opening 41 of the cover panel 40 at an upper
end.

[0031] The battery pack 38 forms a storage space 45 therein by coupling a
lower end of an upper cover 43 having a top-closed and bottom-opened
square pillar shape, which is to be inserted through the insertion hole
39, and an upper end of a lower cover 44 having a top-opened and
bottom-closed square pillar shape, and stores a plurality of batteries 46
therein as shown in FIGS. 4 and 5. In the upper cover 43, an air cleaner
47 is arranged at a top portion, an exhaust duct 48 is arranged at a rear
portion, and a removal hole 50 from which a power line 49 is removed is
provided at a front portion. The battery pack 38 is mounted on the
vehicle body 2 by a sub-frame 51 that is coupled to the respective rear
side members 11 and 12 and the cross member 32.

[0032] The sub-frame 51 includes a ring-like support frame 52 that extends
in a horizontal direction and surrounds an outer periphery of the battery
pack 38. The support frame 52 includes a pair of side member portions 53
and 54 that extend in directions along the respective rear side members
11 and 12, and a front member portion 55 and a rear member portion 56
that extend in the vehicle width direction. The front member portion 55
has a pair of corner portions 57 and 58 that extend diagonally backward
at both ends. The support frame 52 extends in the horizontal direction in
side view and is formed in a substantially-trapezoidal square frame shape
in plan view by coupling the corner portions 57 and 58 at both ends of
the front member portion 55 to front ends of the pair of side member
portions 53 and 54, and coupling both ends of the rear member portion 56
to rear ends of the pair of side member portions 53 and 54.

[0033] The battery pack 38 includes a flange portion 59 that surrounds a
portion coupling the upper cover 43 and the lower cover 44 of the battery
pack 38 in a ring-like shape, and that is coupled to the support frame 52
of the sub-frame 51. The battery pack 38 is arranged at an offset
position toward one side of the pair of side member portions 53 and 54 in
the vehicle width direction on the inner side of the support frame 52. In
the embodiment, the battery pack 38 is arranged at an offset position
toward the left side member portion 54 as shown in FIG. 2. In the support
frame 52, a bracket 60 that couples the front member portion 55 and the
rear member portion 56 is arranged in a space S1 that is formed on the
other side of the pair of side member portions 53 and 54 on the inner
side of the support frame 52 by offsetting the battery pack 38. In the
embodiment, the bracket 60 that couples the corner portion 57 of the
front member portion 55 and the rear member portion 56 is arranged in the
space S1 along the right side member portion 53.

[0034] The flange portion 59 of the battery pack 38 is brought into
abutment against the bracket 60 along the right side member portion 53,
the left side member portion 54, the front member portion 55, and the
rear member portion 56 by inserting the lower cover 44 into the support
frame 52 from above as shown in FIG. 4. The flange portion 59 is coupled
to the bracket 60, the left side member portion 54, the front member
portion 55, and the rear member portion 56 by attachment bolts 61.

[0035] The battery pack 38 coupled to the support frame 52 is arranged in
a space within the cover panel 40 by inserting the upper cover 43 through
the insertion hole 39 formed in the horizontal wall portion 18 from the
lower side of the rear floor panel 14 as shown in FIG. 5, so that the
front member portion 55 as a front side portion and the pair of side
member portions 53 and 54 as both vehicle-widthwise side portions of the
support frame 52 are respectively brought into abutment against the rear
portions 25 and 29 of the respective rear side members 11 and 12, and the
cross member 32.

[0036] In this state, the front member portion 55 as the front side
portion and the pair of side member portions 53 and 54 as the both
vehicle-widthwise side portions of the support frame 52 are respectively
coupled to the cross member 32 and the rear portions 25 and 29 of the
respective rear side members 11 and 12 by coupling portions 62 as shown
in FIGS. 2 and 3. Accordingly, the battery pack 38 is mounted on the
vehicle body 2 by the sub-frame 51 coupled to the rear portions 25 and 29
of the respective rear side members 11 and 12 and the cross member 32.

[0037] As described above, the sub-frame 51 for mounting the battery pack
38 on the vehicle body 2 includes the ring-like support frame 52 that
extends in the horizontal direction and surrounds the outer periphery of
the battery pack 38. Thus, since the sub-frame 51 does not include a
vertical bent portion, the sub-frame 51 can be formed into such a shape
that is difficult to bend in the vehicle vertical direction and is
difficult to compress in the vehicle-longitudinal length when an impact
force is applied to the sub-frame 51 in the vehicle longitudinal
direction.

[0038] Since the front member portion 55 as the front side portion of the
support frame 52 is coupled to the cross member 32 by the coupling
portions 62, the sub-frame 51 transmits a forward force acting on the
support frame 52 to the cross member 32 arranged at a position below the
upper-side edge portions of the bent portions 27 and 31 that connect the
rising portions 26 and 30 and the rear portions 25 and 29 of the rear
side members 11 and 12, and can thereby suppress deformation of the rear
side members 11 and 12 at the bent portions 27 and 31 when an impact
force F is applied from the vehicle rear side as shown in FIG. 3.

[0039] Also, in the sub-frame 51, since the pair of side member portions
53 and 54 as the both vehicle-widthwise side portions of the support
frame 52 are coupled to the rear portions 25 and 29 of the rear side
members 11 and 12 by the coupling portions 62, the rear side members 11
and 12 can be reinforced by the support frame 52, and the rear side
members 11 and 12 can be thereby prevented from being bent in the vehicle
vertical direction when receiving a force in the vehicle longitudinal
direction.

[0040] Thus, the rear side members 11 and 12 are deformed at the bent
portions 27 and 31 that connect the rising portions 26 and 30 and the
rear portions 25 and 29 in the event of a vehicle rear impact, so that
the battery pack 38 can be prevented from colliding with an in-vehicle
part such as the rear seat 20 arranged in front thereof.

[0041] Therefore, in the present invention, the battery pack 38 can be
protected in the event of a vehicle rear impact in the electric car 1 in
which the battery pack 38 is arranged between the rear side members 11
and 12 arranged at the vehicle rear portion.

[0042] The battery pack 38 includes the flange portion 59 that surrounds
the battery pack 38 in a ring-like shape and that is coupled to the
support frame 52 of the sub-frame 51.

[0043] As described above, since the battery pack 38 can be directly
coupled to the support frame 52 of the sub-frame 51 due to the structure
with the flange portion 59 coupled to the support frame 52, the heavy
battery pack 38 can be prevented from moving forward relative to the
support frame 52 to collide therewith in the event of a vehicle rear
impact.

[0044] The support frame 52 of the sub-frame 51 includes the pair of side
member portions 53 and 54, the front member portion 55, and the rear
member portion 56 as shown in FIG. 4. The battery pack 38 is also
arranged at an offset position toward the left side member portion 54 out
of the pair of side member portions 53 and 54 in the vehicle width
direction on the inner side of the support frame 52. By offsetting the
battery pack 38, the space S1 is formed on the right side member portion
53 side out of the pair of side member portions 53 and 54 on the inner
side of the support frame 52. The bracket 60 that couples the front
member portion 55 and the rear member portion 56 is arranged in the space
S1.

[0045] As described above, by arranging the battery pack 38 at an offset
position toward one side (the left side in FIG. 2) in the vehicle width
direction on the inner side of the support frame 52, the space S1 is
formed on the other side (the right side in FIG. 2) in the vehicle width
direction of the battery pack 38, so that an exhaust pipe 63 or the like
coupled to the engine 15 that drives the power generator can be arranged
in the space S1.

[0046] At this point, the bracket 60 that couples the front member portion
55 and the rear member portion 56 is arranged in the space S1 formed on
the inner side of the support frame 52 by offsetting the battery pack 38,
so that the support frame 52 is reinforced by the bracket 60 to thereby
obtain such a structure that is difficult to deform by an impact force in
the vehicle longitudinal direction.

[0047] The filler pipe 22 that extends to the vehicle-widthwise outer side
from the rear side members 11 and 12 is coupled to the fuel tank 21
arranged in front of the battery pack 38 as shown in FIG. 3. The filler
pipe 22 extends to the vehicle-widthwise outer side from the left rear
side member 12 through a space S2 sandwiched between the rear portion 29
of the left rear side member 12 and the left side member portion 54 of
the support frame 52 in the vehicle vertical direction as shown in FIG.
1.

[0048] As described above, in the case of the electric car 1 on which the
fuel tank 21 is mounted in addition to the battery pack 38, the filler
pipe 22 coupled to the fuel tank 21 is arranged in the space S2 that is
prevented from being deformed in the event of a vehicle rear impact by
the support frame 52 of the sub-frame 51, so that the filler pipe 22 can
be protected from collision with other parts.

[0049] The present invention is to protect the battery pack in the event
of a vehicle rear impact in the electric car in which the battery pack is
arranged between the rear side members arranged at the vehicle rear
portion, and can be also applied to a vehicle in which a vehicle part
required to be protected from an impact force in the event of a vehicle
rear impact is arranged in addition to the battery pack.